The character files (along with settings and installed mods, btw) are in a central location.
If you use Win7, it's in (drive):\Users\(username)\AppData\Roaming\runic games\torchlight.
If you use WinXP, it's in (drive):\Documents and Settings\(username)\Application Data\runic games\torchlight.
So it doesn't matter what version you use, the saves, settings and used mods will be the same.
Howdy! And what about mac? I've recently experienced some pretty annoying situation when playing on my old iMac with Leopard. Torchlight crashed during gameplay and then the icon popped out asking me whether I wish to overwrite save game files because the files on my computer appear to be newer than those stored in the cloud. The whole mess stems from the fact that the support for my outdated OS has ended. I knew I had it coming but I kept calm since I've got another, much newer computer. I figured that if I won't be able to play on my old iMac any more, my mac book pro, where I've got the game already installed, will do the job - and it does. The only problem is that I've lost 2 hours progress. And I got really far (just about finishing the game). Instead of agreeing to overwrite when the aforementioned message popped out, I chose to ignore the message ( I guess I was being cautious - not knowing for sure what data it wants to overwrite). When I launched the game again, it threw me to the place where I was 2 hours before. When I understood what I did. it was too late.
I tried backing up the game folders - transferring all the backup files from one computer to another. They had accurate "last modified" date (just minutes before the crash occured) suggesting that the precious latest progress is there. I've replaced all the backup files on new computer ( as well as on the old) with those having the right date hoping -half-heartedly that maybe it will be enough. Unfortunately Steam keeps uploading progress from the cloud - or at least that's what it seems since the new progress is not there. I've thought that maybe the last desperate attempt to regain the progress would be to get the game from gog ( I've got plenty of games from this site and always preffered the drm free anyway), put those files in there and maybe that will make them run. I'm only not sure if it's possible to transfer them at all - and if the old/new progress will be there.
I hope that doesn't sound too complicated. I don't posses the talent for explaining things. My question is really only in the last part - can you guys tell if I will be able to transfer those files from steam saves to gog.. and will that change anything in terms of lost progress.
*What's interesting, achievements that I have managed to unlock in those 2 hours of gameplay are officially unlocked on the steam website - no sign of them when I launch the game, though.